In general, as scalable coding technologies, spatial scalability in which resolutions in layers are different from each other, SNR scalability in which image qualities or bit depths in layers are different from each other, bit depth scalability, view scalability in which plural viewpoint images can be coded, depth scalability in which an image (texture) for viewing and depth information (depth) can be simultaneously coded, 3D scalability (or view scalability plus depth) obtained by combining the view scalability and depth scalability have been known. Regarding scalable coding, images which correspond to a resolution, an image quality, a bit depth, a viewpoint, and a depth are distinguished from each other by using an identifier which is referred to as a layer ID, and are coded.
A scalable technology in which HEVC/H.265 is expanded is known in NPL 1. In NPL 1, a layer of which a layer ID is 0 is referred to as a base layer, and a condition in which coded data of the base layer can be decoded for backward compatibility by a non-scalable decoder (for example, main profile decoder of HEVC/H.265) is applied. This is because the non-scalable decoder can easily perform reproduction in a case where only the base layer is extracted. Thus, even when data is image data subjected to scalable coding, in a layer of which the layer ID is 0, the syntax structure is the same as that of the main profile, and the tool to be used is also the same as that of the main profile. The layer ID is coded as “nah_layer_id” by using the header of a NAL unit.
In the scalable coding, coding is performed by using a dependency relationship between layers, as in a case where an image of a certain viewpoint (certain layer) is predicted from an image of another viewpoint (another layer). Such coding is performed more efficiently than in a case where layers are independently coded. The dependency relationship between layers (data on the presence or the absence of the dependency relationship between layers) is coded based on a video parameter set (VPS). However, in a case where a video having a completely different viewpoint from a certain viewpoint is coded as a subsidiary video, correlation between two images is low, and thus an effect obtained by using the dependency relationship is small. Thus, data which has been coded without using the dependency relationship is decoded more easily. Accordingly, in such a case, a certain layer can be set as a layer (hereinafter, independent layer) which does not depend on other layers, and be coded.
The following methods in which a syntax structure as the data structure of the scalable coding technology for HEVC is changed in accordance with a layer ID are known in NPL 1. (1) A technology in which, by coding profile information and the like using the VPS, the profile information and the like coded by the VPS are omitted in a sequence parameter set (SPS) of an extension layer of which a layer ID has a value other than 0, (2) a technology in which, by coding representation information such as image sizes of a plurality of layers using the VPS, the representation information coded by the VPS are omitted in the SPS of an extension layer of which a layer ID has a value other than 0, (3) a technology in which, by predicting from a scaling list of another layer, coding of the scaling list is omitted in the SPS and a picture parameter set (PPS) of an extension layer of which a layer ID has a value other than 0, and (4) a technology in which, in a case where the layer ID does not have a value of 0, a POC LSB which is not coded in an IDR picture and a BLA picture in which a layer ID has a value of 0 is coded, and a POC which has been also designated in the IDR picture and the BLA picture can be coded, and the like have been known. FIGS. 44 and 45 illustrate a configuration of coded data of an SPS, a PPS and a slice header in case of applying these technologies.